Mexico is poised to overtake Brazil as the top Latin American automobile producer for the first time in more than a decade. Mexico's ascent is fueled in part by auto sales running at the fastest pace in almost eight years in the US, its largest market. The boom coincides with a slump in Brazilian production through June as its domestic demand cools. The diverging fortunes of Mexican and Brazilian auto production reflect the state of their biggest markets. Because of high labor costs and taxes, Brazil-made cars and trucks are too expensive to send abroad and go mostly to local buyers. Mexican factories export 8 out of every 10 cars they produce -- with more than half bound for the US. Mexico's proximity to the US also gives it an advantage, as do labor costs for carmakers that are about 20% of US levels, according to PricewaterhouseCoopers.